Keying arrangement for electric signaling systems



Aug. 31, 1943.

JENER A. G. COOLEY KEYING ARRANGEMENT FOR ELECTRIC SIGNALING SYSTEMSFiled June 11, 1941 INVENTOR AUSTIN G. COOLEY Patented Aug. 31, 1943KEYING ARRANGEMENT FOR ELECTRIC. SIGNALING SYSTEMS Austin G. Cooley,Hudson View Gardens, N. Y.,

assignor, by mesne assignments, to Times Telephoto Equipment Inc.. NewYork, N. Y., a corporation of New York Application June 11, 1941, SerialNo. 397,513

11 Claims.

This invention relates to signaling systems and more especially tokeying control arrangements for facsimile telegraph systems and thelike.

A principal object is to provide a signal control arrangement fortelegraph systems and the like whereby a keying device or a signalreceiving device can be selectively switched from spacing to markingwith a maximum of sharpness between spacing and marking signalconditions.

Another object is to provide a keying arrangement whereby a selectivelyoperable keying member or signal receiving member is switched to markingand spacing positions by current impulses of respectively differentamplitudes and wherein the switching is efiected substantiallycoincident with the change from one amplitude to the other.

Another object is to provide a keying arrangetubes are renderedalternately conductive undercontrol of respective received signals ofdifierent amplitudes. As a result of this arrangement, the push-pulltubes are rendered alternately conductlve and non-conductive for a verysmall difference in amplitude of the two classes of signals so that thepossibility of half-way operation of the said member is avoided.

A further feature relates to an improved circuit control arrangement fora telegraph receiver whereby zero wander of the signal reproducingmember is substantially eliminated.

A further feature relates to a push-pull telegraph signal controlarrangement wherein the sections of the push-pull control are Jointlycontrolled by a single gaseous discharge tube, for example atwo-electrodegas lamp of the neon type or the like.

A still further feature relates to the novel organization. arrangementand relative interconnection of parts which cooperate to produce asimple and efilcient keying control for telegraph systems, wherein theswitching from marking to spacing can be effected with a. difierence inamplitude of as little as & decibel above or below the predeterminedkeying'point.

Other features and advantages not, specifically enumerated will beapparent after a consideration of the following detailed descriptionsand the appended claims.

While the invention will be illustrated and described as embodied in oneparticular kind of signaling system e. g. facsimile telegraph system,

it will be understood that this is done merely for explaining theinventive concept and not by way of limitation. Furthermore, since thevarious elements such as electron tubes, gaseous discharge tubes, keyingdevices, frequency converters and signal receiving and recording devicessuch as facsimile scanners are well-known in the telegraph signalingart, they are illustrated herein is converted into two signal conditionse. g. spac-- ing and marking. For this purpose, device I may be afacsimile or telegraph transmitter which controls the production ofsignal currents of two different levels, the lower level representingfor example marking, and the upper level representing for examplespacing or vice versa. Device I may be a facsimile scanning mechanism ofany known construction such for example as a scanning' drum upon whichis wrapped. the printed matter to be transmitted, and as a result ofwhich the white areas are translated into an audio frequency carrier,for example 1800 c. p. s and the black areas are translated into an 1800c. p. s. carrier of a different amplitude. For a detailed description ofsuch mechanism, reference may be had to my Patent No. 1,719,392 orPatent No. 2,015,742. It will be understood of course that any otherwell-known telegraph keying arrangement may be employed for generatingthe two signal conditions of different relative amplitudes. Thus thedevice I may take the form of an oscillator whose amplitude iscontrolled by a telegraph key or automatic telegraph transmitter inaccordance with respective spacing and marking signals.

At the receiving end of the signaling channel a frequency doubler I ofany well-known type, whereby the 1800 c. p. a. signal amplitudes areconverted into a corresponding 3600 c. p. s. signal amplitudes. The 3600c. p. s. signals are then impressed by means of transformer l on afullwave rectifier tube 5. A small smoothing condenser 6 and a bleedingload resistor I are connected across the output of the rectifier, thepolarity of the rectified current being as indicated in the drawing.Connected in series across resistor I are a gaseous discharge lamp s anda resistor 9. Device 8 may be of any well-known gaseous conduction typesuch as an evacuated bulb containing two electrodes and having a fillingof one or more of the inert gases such as neon. helium or argon. Devicesof this type as. is well-known have a minimum breakdown voltage and donot pass appreciable current until such minimum voltage is applied tothe electrodes.

Associated with device and resistor l are two grid-controlled vacuumtubes "I, ll. While these tubes are shown as of the triode type, it willbe understood that tubes having two or more grids may be employed e. g.shield-grid tubes, pentodes and the like. The resistance 0 is connectedacross the cathode l2 and control grid it through grid its cathode i2when the device 8 is non-conduc tive. The plate electrodes of tubes l0and ii are connected in balanced relation through two operating windingsi1 and i8 and through a battery or plate supply ll.

Associated with windings ll, II, is an armature or bar 20 which ismounted for swinging movement and is adapted to be actuated in onedirection or the other depending upon which of the windings I1, is, isenergized. The member 20 cooperates with any well-known form oftelegraph signal recorder schematically illustrated by the rotating drum2|. Merely by way of example, drum 2! (Fig. 2) may have around itsperiphery in helical form a rib or knife edge 25 and the member 20 maycarry a knife edged bar 22 which extends substantially parallel to theaxis of drum II, a suitable recording web or tape II being positionedbetween bar 22 and the knife edge on drum 2!. when the member 20 is inspacing position, bar I! is clear of the recording paper. when a markingsignal is received, bar I! is moved to engage the recording paperwhere.- upon a suitable mark is made thereon. Thus bar 21 may beconnected to one side of a source of recording potential and the knifeedge on drum 11 may be connected to the other side oi this source, sothat when the bar 1! is moved to marking. the recording paper is actedupon either by an electric discharge, spark. or by current conducticnthrough the paper to produce the record. It will be understood thatmember 20 may be used to control the recording when of any wellknowntype of telegraph syphon recorder, or if desired the member 20 may beused itself as a keying control for repeating spacing and markingsignals to another point.

In the arrangement illustrated, member 20 and windings l1, I8, may formpart of any wellknown construction such as used in radio loud L, thesignals are passed through a filter or ad- Justable attenuator pad 2 andthence through speakers of the movable armature type, the armature beingconnected to member 20. As an alternative, members ll, it and 20 mayconstitute any. well-known form of telegraph relay construction. a

The tube i0 and winding H are the marking control for moving member 20to marking position, while tube I I and winding it are the spacingcontrol for moving member to spacing position. Tubes II and H areconnected in pushpull relation for alternate on-and-of! control which isdetermined primarily by the breakdown of the gaseous device I. For, lowlevel signals transmitted from device I, corresponding for example tomarking, the device 8 does not receive suilicient voltage to break itdown, so that the grid it is at substantially zero potential withrespect to its cathode i2. and therefore considerable plate currentpasses through winding II. The plate current through winding i1 holdsthe member 20 to marking. Under this condition the plate current of tubell flows through resistor is thus applying a relatively strong negativebias to grid 23 with respect to its cathode 24 blocking off platecurrent through tube H. Member 20 therefore\ remains in marking positionso long as the marking signal condition continues.

When an increased signal level, corresponding to spacing, is transmittedfrom device I, a suillcient voltage is developed across device 8 tobreak it down and current therefore passes through resistor 0. Thevoltage drop developed in resister 8 applies a negative bias to grid itthereby blocking tube It. The blocking bias on grid 23 is simultaneouslyremoved and tube ll becomes conductive whereby winding i8 is enersizedto hold member 20 in spacing position. The plate current of tube llflowing through resistor It produces a slight negative bias on grid 23but not suillcient to block tube II. It will be understood of coursethat tubes I0 and H can be chosen of such characteristics that thecurrent flowing through winding [1 for spacing is equal to the cu1rentflowing through winding 18 for marking.

However, preferably the tubes and associated circuit elements areproportioned so that a slightly greater current flows for marking thanfor spacing because during marking there is amechanical load on themember 20 while no load exists during spacing. For extremely fast actionin switching from marking to spacing and vice versa. the capacity 8should be very small. If it is desired to cause the device 8 to breakdown at a lower voltage than normally provided across resistor '1, ablessing voltage can be connected in series with device l at anyconvenient point in the circuit.

The manner of operation is along the following lines. Assuming that thedevice i is transmitting an 1800 c. p. s. marking signal, this signal isthen amplified, and after suitable amplification it is passed throughthe attenuator pad 2 to adjust the signal level and thereupon the signalis passed through a frequency doubler 3, thus Droviding a 3600 c. p. a.signal of marking amplitude. This signal after passing the rectifier 5is or insuiiicient voltage to cause breakdown of device 8, and thereforegrid II is at substantially the same potential as cathode l2 and amarking current flows through winding I! to cause member 20 to operatebarn to make a mark on the recording tape or web. In the case of arecorder oi the type where the drum I has a helically arranged knifeedge 25 intersecting cooperation with bar 22, the drum 2| willbeconstantly rotating in synchronlsm with the corresponding drum orscanning portion of device I while the recording paper is stationaryexcept for line-feeding movementwhich may be controlled as explained insaid Patent No. 1,719,392. The eiIect of rotation of the helical knifeedge with respect to the bar 22 is, as is well-known in the facsimileart, to scan the'recording tape in successive transverse parallel lines.As each transverse line is thus scanned, the tape is fed in thedirection of its length a distance corresponding to a line thickness soas to present the next line for scanning.

Upon the receipt of a spacing signal, the voltage developed acrossdevice 8 rises to the point where device 8 becomes conductive thusblocking tube and rendering tube' ll conductive and holding member 20 inspacing position.

.With the foregoing arrangement, I have found that the operation ofmember 20 is so sharp that a swing of as little as decibel above orbelow the critical keying potential is all that is required to switchfrom markihg to spacing and vice versa. If even sharper control isrequired, it may be had by removing condenser 6 if some vibration of thearm 20 can be tolerated when it is on the spacing side and if itsmechanical inertia is made suiiicient to prevent it from swinging overto marking side with condenser 6 removed. Ihavefound it possible toobtain complete marking and spacing recordings on the web 26 with asignal voltage variation of less than one part in twenty live.

If condenser 6 is large, it is necessary that the voltage across theresistor 1 swing a little more than the difference between the strikingand operating voltage characteristic of the gas tube 8. Such a largeswing is not necessary if the filtering of the rectifier output isreduced or eliminated since the dip in the signal (lower side of theripple) drops low enough to deionize the tube 8, 3600 times per secondin the case illustrated. If the peak signal across 1 is just a triflebelow the striking voltage of 8, the signal will be recorded as marking.If the peak signal across I is just a trifle above the striking voltageof 8,'the tube will start conducting at the peak and during that portionof the cycle which is above the operating portion of the tubecharacteristic. During this time the armature 20 is moved to spacing. By

properproportioning of mechanical inertia, travel of armature, andspring biasing, it is possible to prevent the arm 22 from reaching themarking position during the remaining portion of the cycle. It will beunderstood of course that various changes and modifications may be madein the particular embodiment disclosed without departingfrom the spiritand scope of the invention. Thus while a frequency doubler is shown,that may be dispensed with and the received frequency can be applied tothe keying control circuit. In the case where channel L is a radiochannel, a suitable detecting arrangement will be used at the receivingend to detect the original marking and spacing signals.

What I claim is:

1. In an electric signaling system, a signal device having a member tobe selectively set in at least two signal-controlled positionscorresponding to two diiierent signals, a pair of control windingsassociated with said -member each arranged to be energized in responseto a corresponding one of said signals, a pair of grid-controlled vacuumtubes having their output circuits connected in divided relation to saidwindings, means responsive to one of said signals for biassing thecontrol grid of one of said tubes substantially to plate current cutofiand to maintain it so biassed as long as said signal continues, andmeans responsive to the other of said signals to bias the control gridof said other tube to substantial plate current cutoil and to maintainit so biassed as longas said other signal continues, and means wherebythe current inthe output circuit of one tube during the reception of oneof said signals is greater than the current in the output circuit of theother tube during the reception of the other signal.

'2. A signal responsive arrangement for responding selectively to highand low amplitude signals comprising a signal device movable to twopositions corresponding respectively to said high and lowamplitudeslgnals, first and second gridcontrolled vacuum tubes adaptedto be alternately biassed to plate current cutoif, means to impress bothsaid signals directly only on the control grid of said first tube, thecontrol grid of said second tube deriving its grid potential from theplate current of the first tube, a D. C. bias circuit for the grid ofsaid first tube for normally biassing said first tube to passsubstantial plate current so long as low amplitude signals are beingreceived, and a device which responds only to the high amplitudesignals, said device being connected to said D. C. bias circuit tochange the control grid bias of said first tube to plate current cutoff,and thereby simultaneously to change the control grid bias of saidsecond tube to allow plate current to pass.

3. In an electric signaling system, a signal device having a member tobe set in at least two signal-controlled positions in response to twodifierent signals, first and second grid-controlled tubes having theiroutput circuits connected in divided relation to control the selectivesetting of said member, means responsive to one of said signals to biasthe grid of the first tube to pass I substantial plate current and tomaintain it so biased as long as said signal continues, means controlledby said plate current to bias the grid of the'second tube to substantialplate current cutoff and to maintain it so biased so long as said signalcontinues, and a gaseous conduction tube responsive to the other signalto bias the grid of the first tube to substantially plate current cutofiand to maintain it so biased so long as said other signal continues,whereby said other tube substantially immediately passes plate currentin response to said other signal.

4. In an electric signaling system, a signal device having a member tobe selectively set in at least two signal-controlled positions, firstand second grid-controlled vacuum tubes having their output circuitsconnected in divided relation to control the selective setting of saidmember, and means to bias said tubes successively to substan-,

tial plate current cutofl' in response to successive signals ofdifferent characters, the biasing of each tube being'maintained so longas the corresponding signal is being received, the last-mentioned meansincluding a gaseous discharge tube which applies a cutoff bias to thefirst tube only in response to one of said signal conditions, and alsoincluding a connection from the output circuit of the first tube toapply a cutoti bias to the second tube during the cessation of said oneor the signal conditions.

5. In a telegraph signaling system, a telegraph signal device having amember to be selectively set to marking and spacing positions inaccord,- ance with signal voltages of different relative amplitude butof the same polarity, first and 4 second grid-controlled vacuum tubeshaving their plate circuits connected to control respectively theselective setting of said member, means to apply both signals so thatthe conductivity of only the first tube is controlled directly byreceived marking and spacing signals, the conductivity of the secondtube being controlled by the plate current of the first tube, and atwo-element gaseous discharge tube responsive only to one of said signalvoltages for controlling the application of a cutoi! grid bias to saidfirst tube.

6. In a telegraph signaling system, first and second grid-controlledvacuum tubes, means normally connecting the grid of the first tube toits cathode whereby said first tube normally passes substantial platecurrent, means responsive to a telegraph signal to apply a plate currentcutofi bias to the grid of said first tube including a twoelementgaseous discharge tube which becomes conductive only in response to saidsignal, and means responsive to the fiow of plate current in said firsttube for biassing the second tube to plate current cutofl and formaintaining it so biased.

7. In a telegraph signaling system, means for producing marking andspacing signals of difierent amplitudes, first and secondgrid-controlled vacuum tubes, the second tube being normally biassed tosubstantial plate current cutoi! while the first tube is passingsubstantial plate current, a grid bias resistor tor the second tube,said resistor being connected in the plate-cathode circuit of the firsttube, means for blocking the signal of lower amplitude from afiectingthe bias on said second tube, and means responsive to the higheramplitude signal to render said first tube substantially non-conductivewhile simultane-- ously rendering the second tube conductive.

8. A telegraph system according to claim 7 in which there is abiasresistor in the grid circuit of said first tube and said blocking meansinveludes a gaseous discharge tube ior controlling 2,828,056 stantialplate current, a gaseous discharge tube in series with said resistancebut normally noncondu'ctive for one signal condition, means responsiveto another signal condition to render said gaseous tube conductive andthereby to apply a blocking bias through said resistance to said firsttube, and means responsive to the application of said blocking bias tosaid first; tube to remove-a blocking bias from the second tube.

10. A telegraph keying system comprising means to receive signals or oneran ers amplitudes representing one signal condition and to receivesignals of a difi'erent range oi amplitudes representing a difierentsignal condition, a twoelement gaseous discharge tube to which saidsignals are applied, said gaseous discharge tube being non-conductive solong as one or said conditions continues and being conductive so long asthe other of said signal conditions continues, a bias resistorresponsive to current through said gaseous tube to develop apredetermined potential drop therein, a first grid-controlled vacuumtube which is normally biassed to pass substantial plate current andmeans connecting said resistor to the grid of said first grid-controlledvacuum tube to apply a plate current cutofi bias thereto when saidgaseous tube becomes conductive, a second grid-controlled vacuum tubehaving a grid bias resistor through which the plate current or the firstvacuum tube passes, said vacuum tubes and bias resistors being connectedso that when said first tube passes substantial plate current the platecurrent of the other is substantially reduced.

11. A telegraph keying system comprising a first grid-controlled vacuumtube, a second gridcontrolled vacuum tube, a resistance in. the platecircuit r the first tube, said resistance also being connected in thegrid circuit of the second tube to bias it'substantially to platecurrent cutoii! under control of the plate current or the first tube,means including a bias resistance connectpasses substantial platecurrent, and a source or signal voltage and a two-element gaseousdischarge tube connected in series with thelastmentioned biasresistance, said gaseous discharge tube being conductive only inresponse to'telegraph signals oi a predetermined minimum amplitude.

AUSTIN G. COOLEY.

